Looking down the tube of my 12" dob, I've noticed the primary mirror had this kind of 'fog' on one half.
It looks like someone has breathed on it causing a fog, and compared to the clean/normal side it loses some clarity.
So today I decided to take out the cell, inspect a little more and give it a clean (help from the articles
here), but the mark is still there.
The scope is only 8 months old. What is this 'fog' and is there anything apart from the processed described above that I can do to clean/remove it?
Thanks
